If the three letters H-P-V make you recoil, they shouldn't. Chances are, you have been infected by one or more types of the human papillomavirus (HPV) and didn't even realize it. In fact, according to the U.S. Centers for Disease Control and Prevention (CDC), most people will become infected by at least one type of HPV at some point in their lives. The CDC reports that 79 million people are currently infected with HPV.

The good news is, in most cases, HPV causes no symptoms or health problems and goes away on its own. HPV is a skin cell virus with more than 100 identified types. That includes low-risk types that may cause genital warts and high-risk types that may cause precancer and cancer.

If HPV causes cells to become abnormal, most return to normal on their own. However, when high-risk types of HPV persist, precancer and cancer may occur. The American Cancer Society estimates that about 13,170 cases of invasive cervical cancer will be diagnosed in the United States in 2019, killing about 4,250 women.

HPV is the cause of nearly all cases of cervical cancer, but cervical cancer is preventable. Screening by Pap and HPV testing can detect precancerous changes that can be treated to prevent cancer from developing.

HPV can also lead to anal cancer in both men and women, a cancer that affects about 5,530 women and 2,770 men per year and causes 760 deaths in women and 520 in men and is on the rise. Notably, anal intercourse is not required for HPV to infect the anal skin cells.

Other health problems can result from HPV infection as well, including genital warts; recurrent respiratory papillomatosis, a rare condition where warts grow in the throat of babies who have been delivered through the birth canal of a mother with genital warts; and other less common but potentially serious cancers, including cancer of the vulva, vagina and penis, and oropharyngeal cancer, a type of head and neck cancer that affects the back of the throat, base of the tongue and the tonsils.

The HPV family of viruses is called papillomavirus because they tend to cause warts, or papillomas—benign (noncancerous) tumors. There are more than 150 strains of HPV and at least 40 HPV types that can infect the anus or genitals. Warts may appear on the hands and feet or on the genital and anal areas. The strains of HPV that cause warts to grow on hands and feet, however, are rarely the same type that cause warts in the genital and anal areas.

The high-risk HPV subtypes most likely to cause cancer are HPV-16, HPV-18, HPV-31, HPV-33, HPV-45, HPV-52 and HPV-58. HPV-16 and HPV-18 cause 70 percent of cervical cancer and HPV 16 causes 90 percent of anal cancer. (HPV 16 is also seen as a cause of some oropharyngeal cancers.)

Two types of HPV—HPV 6 and 11—cause 90 percent of genital warts, though they have almost no risk of causing cancer and therefore are commonly referred to as low-risk types.

There is currently one HPV vaccine approved by the U.S. Food and Drug Administration (FDA), called Gardasil 9, which can protect women against the HPV types that cause most cervical cancers. Gardasil 9 also protects women against vaginal and vulvar cancers and protects both men and women against most genital warts and anal cancers. (See Prevention section for more information.)

In addition to the HPV vaccine for primary prevention, the Pap test and the HPV test are important screening tools to prevent cervical cancer in women. When combined with a Pap test in women age 30 and older, the HPV test is better at identifying women at risk for developing cervical cancer than the Pap test alone. The HPV test is also approved by the FDA to be done alone for women 25 and older, however, most medical organization guidelines call for its use alone in women 30 and older. (See Diagnosis section for more information.) There is no FDA-approved HPV screening test for men.

Because of early detection and treatment of cell changes, the death rate for cervical cancer has decreased by more than 50 percent over the last 40 years.

Conversely, the number of new anal cancer cases has been steadily rising, with most cases occurring in adults. The average age at diagnosis is in the early 60s. Anal cancer affects women more often than men.

How does HPV spread?

HPV spreads via skin-to-skin contact with an HPV-infected area. Infections can be subclinical, meaning the virus lives in the skin without causing symptoms. Hence most people with HPV do not know they have it or that they could spread it. For a person exposed to a partner who has a low-risk genital wart–causing strain of HPV, such as HPV 6 or 11, it takes about six weeks to three months for genital warts to appear. However, most people who are infected by HPV 6 and 11 do not develop genital warts. The most common HPV infections are by high-risk types, and there are no visible symptoms. These infections can only be detected on HPV tests or because of abnormal cell changes detected on Pap tests.

Condoms don't always protect against the virus because the virus can grow on areas of the genitals not covered by a latex barrier.

It is thought that HPV 6 and 11 may be more easily spread to partners when genital warts are present then when they have been cleared. Therefore, avoiding contact with a new partner until warts are cleared is recommended. HPV most easily gets to the female cervix through penetrative intercourse; however, any skin-to-skin contact may allow the virus to spread.

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